The ability to compare objects according to discrete dimensions such as size, color or shape seems basic to human intelligence. However, developmental research indicates that knowledge of dimensions is complex and emerges gradually throughout the preschool and early school years. This reserach investigates a componential model in which an understanding of identity, wholistic similarity, attribute, dimension, direction, intensive order, and continuity comprises the structural core of dimensional knowledge. The proposed project tests the developmental independence of these components and their order of acquisition. Performance in verbal and nonverbal tasks will be compared to provide a complete description of the development of dimensional concepts. Certain aspects of this growth may reflect experience with objects, other aspects may reflect experience with language. Children aged 2-8 will be the primary participants. In addition language-disordered children and adults will participate in some studies. The experiments of Project I compare children's conceptual knowledge of relations and their acquisitions of the words that refer to relations. Conceptual knowledge will be assessed in an immitation task that requires abstract inferences about relations. Word knowledge will be measured by verbally asking children to select objects specified by attribute or relation, e.g. "Find the big one", "Which two are the same." Project II examines children's knwoledge of relations via learning tasks, reasoning tasks and seriation tasks. Project III investigates the development of relational language and relational concepts in language-disordered children and in children learning a first language other than English. Project IV investigates the perception of relations in children and adults in order to understand the development of the mechanisms that underly the developmental growth in relational knowledge. Since aspects of dimensional knowledge are crucial components of mathematics and inferential reasoning, this project will contribute to educational programming for all children and special populations such as that of language-disordered children.